Vehicle data communication

ABSTRACT

A communications system for providing data communication to a vehicle ( 10 ), the communications system comprising: a mobile transport layer proxy ( 150 ) located on the vehicle; a parent transport layer proxy ( 170 ) located remote from the vehicle; the mobile transport layer proxy being configured to: accept a transport layer connection with a host device ( 32, 33 ), the transport layer connection being addressed to a remote server ( 160 ); and communicate with the parent transport layer proxy via multiple paths using a multipath transport layer protocol to communicate on behalf of the host device whilst identifying as the mobile transport layer proxy; and the parent transport layer proxy being configured to: communicate with the mobile transport layer proxy using the multipath transport layer protocol; and communicate with the remote server whilst identifying as the parent transport layer proxy to communicate on behalf of the mobile transport layer proxy to permit the host device to communicate with the remote server.

FIELD OF DISCLOSURE

This invention relates to a communications system for providing datacommunication to a vehicle. In one example, the vehicle is a train.

BACKGROUND

Vehicles such as cars, buses and trains are examples of passengercarrying vehicles. The passengers that are carried by those vehiclestend to possess devices that connect to the internet to access servicesprovided by remote servers. For example, the passengers may access anemail server to check whether they have any new email or access a webserver to download web pages. Those devices may be equipped with awireless network adapter that allows the device to connect to a networkthat provides access to the internet. The wireless network adapter couldbe a 3G, 4G or, more generally, cellular modem that can connect to thebase stations of a cellular network operator. The wireless networkadapter could also be a Wi-Fi adapter.

It is becoming more common for passenger carrying vehicles to connect tothe internet and then share this connection with the passenger's deviceson-board the vehicle. This shared connection can be used to allowdevices that only have a Wi-Fi or wired network adapter to connect tothe internet. It is also done because such passenger carrying vehiclesgenerally travel through less densely populated areas where cellulardata connections can be of low quality or low signal strength. Theconstruction of the vehicle can also inhibit or reduce the quality ofthe signal from a base station that can be received by a passengerdevice inside the vehicle. These points can make it difficult forindividual user devices to connect directly to the cellular networks.

Where the vehicle shares a connection among the passengers, the vehicleis equipped with a router that connects to at least one antenna on theexternal of the vehicle for connecting to wayside base stations. Thesebase stations may be cellular base stations provided by cellular networkoperators or other wireless base stations such as Wi-Fi base stations.The router will also be equipped with at least one antenna on theinternal of the vehicle and/or connected to a wired network which enduser devices can use to connect to the Internet via the on-vehiclenetwork provided by the router. The router may be comprised of more thanone part to provide these connections, for example it may be a cellularmodem, a wireless access point and a packet router connected together.

As the vehicle moves along its path of travel, the vehicle will move outof the communication range of certain base stations and in to thecommunication range of other base stations. The router will thereforeneed to disconnect from the out of range base station and connect to onewithin range to continue to provide an internet connection to the enduser devices. To aid in this connection jump from one base station toanother base station, the router can be equipped with at least twoexternal antennas for connecting to the wayside base stations. Therouter can then establish a connection to the new base station using oneantenna whilst still having a connection via the other antenna to theold base station. The router can then handover from one base station toanother without a drop in connection.

As there are multiple cellular network operators within a given countrythere are normally multiple base stations that serve a particular area.Also, even within one cellular network operators network there will beoverlap between the coverage areas of the base stations. This can beused as described above to provide a handover from one base station toanother without a drop in connection. However, it would be desirable tobe able to make use of the connections provided by the multiple basestations, especially as the data connection provided by a single basestation may be of low bandwidth and/or shared between many users. Such asystem introduces difficult routing conditions for the on-board routeras each data connection is identified separately and so makes itdifficult for the on-board router and a server on the internet tocommunicate in a way that makes efficient use of the multipleconnections.

Therefore, there is a need for an improved communication system thatallows devices on-board a vehicle to communicate with remote serversusing multiple connections.

BRIEF SUMMARY

According to the present invention there is provided a communicationssystem for providing data communication to a vehicle, the communicationssystem comprising: a mobile transport layer proxy located on thevehicle; a parent transport layer proxy located remote from the vehicle;the mobile transport layer proxy being configured to: accept a transportlayer connection with a host device, the transport layer connectionbeing addressed to a remote server; and communicate with the parenttransport layer proxy via multiple paths using a multipath transportlayer protocol to communicate on behalf of the host device whilstidentifying as the mobile transport layer proxy; and the parenttransport layer proxy being configured to: communicate with the mobiletransport layer proxy using the multipath transport layer protocol; andcommunicate with the remote server whilst identifying as the parenttransport layer proxy to communicate on behalf of the mobile transportlayer proxy to permit the host device to communicate with the remoteserver.

The parent transport layer proxy may be configured to accept aconnection with the mobile transport layer proxy that is addressed tothe remote server. The parent transport layer proxy may be configured tocommunicate with the mobile transport layer proxy via multiple pathsusing the multipath transport layer protocol.

The mobile transport layer proxy may be configured to accept thetransport layer connection with the host device by intercepting atransport layer session originating from the host device that isaddressed for the remote server. The mobile transport layer proxy may beconfigured to accept the transport layer connection with the host deviceby masquerading as the remote server and terminating the transport layersession originating from the on-board device at the mobile transportlayer proxy.

The parent transport layer proxy may be configured to intercept atransport layer session originating from the mobile transport layerproxy that is addressed for the remote server. The parent transportlayer proxy may be configured to masquerade as the remote server andterminates the transport layer session originating from the mobiletransport layer session at the parent transport layer proxy.

The mobile transport layer proxy may be connected to a plurality ofradio transceivers, each radio transceiver is configured to establish arespective wireless data connection to equipment located remote from thevehicle independently of the other radio transceivers, and each one ofthe data connections may be one of the multiple paths. The plurality ofradio transceivers may be located on the vehicle. Each radio transceivermay establish the respective data connection with a different basestation located remote from the vehicle. The base station may compriseone of a number of wayside base station next to a path taken by thevehicle. The vehicle may be a train and the path taken by the vehiclemay be a railway track. The base station may be wireless base stations.The base station may be cellular base stations.

The communication system may comprise a mobile router located on thevehicle, the mobile router may comprise the plurality of radiotransceivers. The mobile transport layer proxy may form part of themobile router and the mobile router may communicate with the parenttransport layer proxy via multiple paths using the multipath transportlayer protocol.

At least one separate subconnection of the multipath transport layerprotocol may be established over each of the multiple paths.

The mobile transport layer proxy may be configured to divide a datastream for transmission to the parent transport layer proxy in to anumber of substreams at least equal to the number of paths and send aduplicated or different substream over each of the subconnections. Aseparate subconnection of the multipath transport layer protocol may beestablished over each of the multiple paths. The mobile transport layerproxy may be configured to divide a data stream for transmission to theparent transport layer proxy in to a number of substreams equal to thenumber of paths and send a different substream over each of thesubconnections. The substreams may be formed of data packets and themobile transport layer proxy may be configured to incorporate a datastream identifier in to each data packet, the data stream identifierindicating the position of the data packet in the data stream.

The parent transport layer proxy may be configured to divide a datastream for transmission to the mobile transport layer proxy in to anumber of substreams at least equal to the number of paths and send aduplicated or different substream over each of the subconnections. Aseparate subconnection of the multipath transport layer protocol may beestablished over each of the multiple paths. The parent transport layerproxy may be configured to divide a data stream for transmission to themobile transport layer proxy in to a number of substreams equal to thenumber of paths and send a different substream over each of thesubconnections. The substreams may be formed of data packets and theparent transport layer proxy may be configured to incorporate a datastream identifier in to each data packet, the data stream identifierindicating the position of the data packet in the data stream.

The multipath transport layer protocol may be Multipath TransmissionControl Protocol (MPTCP). The separate subconnections may be separatesubflows of the MPTCP. The data stream identifiers may be data sequencenumbers.

The parent transport layer proxy may not move with the vehicle. Theposition of the mobile transport layer proxy may be fixed relative tothe vehicle. The mobile transport layer proxy may connect to the hostdevice via a wireless connection.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described by way of example withreference to the accompanying drawings. In the drawings:

FIG. 1 shows a schematic diagram of a communication system.

FIG. 2 shows a schematic diagram of the communication of data between anend-user device and a remote server using the communication system.

DETAILED DESCRIPTION

The following description is presented to enable any person skilled inthe art to make and use the invention, and is provided in the context ofa particular application. Various modifications to the disclosedembodiments will be readily apparent to those skilled in the art.

The general principles defined herein may be applied to otherembodiments and applications without departing from the spirit and scopeof the present invention. Thus, the present invention is not intended tobe limited to the embodiments shown, but is to be accorded the widestscope consistent with the principles and features disclosed herein.

The present invention relates to a communications system for providingdata communication to a vehicle, such as a train. The vehicle isprovided with a mobile router containing a mobile proxy server that canconnect using a multipath transport layer protocol to a parent proxyserver for requesting and receiving internet based data on behalf of anon-board end user device that is connected to the mobile router. Theparent proxy server requests and receives the internet based data onbehalf of the mobile proxy server. The mobile proxy server and theparent proxy server are able to communicate with each other overmultiple, distinct paths using a multipath transport layer protocol suchas the Multipath Transport Control Protocol (MPTCP) as described in theInternet Engineering Task Force (IETF) RFC 6824. Whilst the specificexample of MPTCP is given and discussed in the examples below, it willbe readily apparent that an alternative multipath transport layerprotocol that permits communications between devices over multiple,distinct paths could be used.

FIG. 1 shows a schematic diagram of an example communication system inaccordance with the present invention. In FIG. 1, a train 10 isillustrated as travelling along a track 11. This is given as an exampleand it will be readily apparent that the communication system describedbelow could equally be used on another type of vehicle such as a coachor car travelling along a road.

The train 10 is provided with a mobile router 20. This mobile router 20is described as mobile in the sense that, whilst its position is fixedrelative to the train 10, the mobile router 20 is moves relative to theground when the train 10 is mobile. The mobile router 20 is equippedwith an antenna 31 that enables the mobile router 20 via a radiotransceiver to accept wireless, Wi-Fi connections from end-user devices32, 33. The mobile router 20 can also be attached to wired network 36for wired connection to the end-user devices 32, 33. The end-userdevices 32, 33 connect to the mobile router 20 using respective antenna34, 35 via respective radio transceivers.

The antenna 31 that the end-user devices 32, 33 connect to may bedescribed as an internal antenna. This is to mean that it will generallybe used to connect with devices such as the end-user devices 32, 33 thatare located on the inside of the vehicle 10. However, the antenna 31itself does not necessarily need to be located on the inside of thevehicle nor does it solely have to be used to connect with deviceslocated on the inside of the vehicle.

The mobile router 20 is also equipped with at least two antennas 40, 50that are connected to respective radio transceivers to provide arespective data connection to ground-based equipment independently ofthe other radio transceivers. The radio transceivers can include: (a)one or more transceivers each of which can independently establish adata connection 60, 70, 75 with one of a number of wayside base station80, 90, 100 next to the railway track; and (b) one or more cellulartransceivers each of which can independently establish a data connection60, 70, 75 with cellular base stations 80, 90, 100 of telephoneoperators. The base stations 80, 90, 100 are connected to respectivenetwork connections 110, 120, 130 to allow communication with serverslocated on the internet.

In the case of the one or more cellular transceivers these can be in theform of 3G or 4G cellular modems which each connect to a cellular basestation 80, 90, 100 to establish the data connection 60, 70, 75. In thecase of a 4G cellular modem these could operate according to, forexample, LTE, WiMAX or HSPA+ standards.

The mobile router 20 can establish data connections with a data centre140 using the cellular data connections 60, 70, 75 and the respectivenetwork connections 110, 120, 130.

As shown in FIG. 1, mobile router 20 can establish data connections witha data centre 140 using data connections that are established by a slaverouter 180. In this embodiment the mobile router 20 is connected toslave router 180. This connection can be made by a wired data connection36 or alternatively by a wireless connection. The slave router 180 isequipped with at least one antenna 55 that is connected to a respectiveradio transceiver to provide a data connection to ground-based equipmentindependently of the other radio transceivers, in the slave router 180and the mobile router 20. It can be advantageous to place the mobilerouter 20 at one end of the vehicle 10 and the slave router 180 at theother end of the vehicle 10. When the vehicle is a long vehicle such asa train, this means that the antennas at opposite ends of the train 10will experience different network operating conditions and/or be able toconnect to different base station 80, 90, 100. This means that themobile router 20 can make use of as many different base stations aspossible, thus improving the quality of the link between the train 10and the data centre 140.

The mobile router 20 functions as a mobile proxy 150 that intercepts TCPuser sessions that originate from the end-user devices 32, 33 and areaddressed to a remote server 160 on the internet. The mobile proxy 150works at the transport layer of the data connections when it interceptsthe TCP user sessions. The transport layer is otherwise known as layer 4of the Open Systems Interconnection (OSI) model. The TCP user sessionsare more generally transport layer connections.

In some cases, the local proxy 150 may be a separate device that isconnected to the mobile router 20. For example by a wired connection.

When the mobile proxy 150 intercepts the TCP user sessions thatoriginate from the end-user devices 32, 33, the local proxy 150masquerades as the remote server 160 and so the TCP user session fromthe end-user device 32, 33 terminates at the mobile proxy 150. Themobile proxy 150 therefore accepts connections that are addressed for aremote server 160 and thus terminates those connections at the mobileproxy 150. The local proxy 150 has the ability to intercept those TCPuser sessions because the router 20 passes external network connectionrequests to the local proxy 150 for inspection. External networkconnection requests are requests by the end-user devices 32, 33 forresources that are identified as being located in a network that isremote from the local network on-board the train. These external networkconnection requests could be requesting information from remote serversthat are located on the internet.

The mobile proxy 150 is configured to communicate with a remote proxy170 that is located in the data centre 140. The mobile proxy 150 isconfigured to request from the remote proxy 170 any data that is locatedin the remote, external networks. In this way the remote proxy 170 actsas a parent proxy for the mobile proxy 150. In a similar way to themobile proxy 150 terminating the end-user device connections at themobile proxy 150, the parent proxy 170 terminates the mobile proxy 150transport layer data connections at the parent proxy 170.

When an end-user device 32, 33 sends a request for data from remoteserver 160, as described above, the mobile proxy 150 masquerades as theremote server 160 and terminates the transport layer connection from theend-user device 32, 33 at the mobile proxy 150. The mobile proxy 150then requests the data requested by the end-user device 32, 33 from theparent proxy 170 on behalf of the end-user device 32, 33. The parentproxy 170 masquerades as the remote server 160 and terminates thetransport layer connection from the mobile proxy 150 at the parent proxy170. The parent proxy 170 then initiates a connection with the remoteserver 160 and requests the data from the remote server 160 on behalf ofthe mobile proxy 150 and, indirectly, for the end-user device 32, 33.

The local proxy 150 is capable of communicating using multipathtransport layer protocol connections, for example using Multipath TCP(MPTCP) connections. The parent proxy 160 is also capable ofcommunicating using multipath transport layer protocol connections, suchas MPTCP connections. Therefore, the local proxy 150 and parent proxy160 are configured to communicate with each other using a multipathtransport layer protocol such as MPTCP.

As discussed above, the mobile router 20 can establish data connectionswith the data centre 140 using the cellular data connections 60, 70 andthe respective network connections 110, 120, 130. This means that themobile proxy 150 can establish multiple data connections with the remoteproxy 170. Each of these separate cellular data connections forms aseparate path for the MPTCP connection. Therefore, when there are twoseparate cellular data connections there will be two separate paths, onefor each of the data connections. The wireless data connections, thatare not necessarily cellular data connections, can be used in acorresponding way.

The MPTCP protocol can establish a separate subflow over each of theseparate paths. The MPTCP protocol can also establish more than oneseparate subflow over a given path dependent on network conditions. Asthe quality of a particular path decreases the subflow established overthat path may be dropped. If it is detected that the quality of aparticular path has improved, or a new path established then a subflowmay be established over that path. Within the MPTCP protocol, a subflowis an individual TCP connection that is established between the twocommunicating devices over that particular path. Therefore, separate TCPconnections are established by the MPTCP connection, and so by the twocommunicating devices, over each of the paths that are being used toform the connection. Within an individual subflow, the normal TCPparameters are used to handle the data transactions within thatindividual TCP connection. For example, data transferred over anindividual subflow will be acknowledged using a standard ACK parameter.The data transactions that occur at the individual subflow level arealso monitored at the MPTCP level. For example, there will also be anacknowledgement that occurs at the MPTCP level to acknowledge that asegment of data has been successfully transmitted over one of thesubflows.

The separate, multiple paths from the mobile router 20 to external,non-onboard networks are identified as being separate paths because eachpath has different network layer addresses. The each interface thatcommunicates via a radio transceiver and antenna has a distinct networklayer address. The distinct network layer address can be a distinct,different IP address.

MPTCP provides two different ways for these separate paths to beidentified to the communicating device at the other end of theconnection. The first identification method is for the device with morethan one separate connection to initiate a connection from each of theother connections to the remote device. This initiation processestablishes the separate subflow with the remote device. The secondidentification method is for the device with more than one separateconnection to advertise to the remote device that the device has morethan one separate connection and is capable of communicating over thosemultiple connections. MPTCP provides for a TCP option that announcesadditional addresses on which a host can be reached. This addressmessage tells the remote device to add a network layer address to thelist of addresses that the local host can be used to communicate withthe local host.

Data is transferred over an MPTCP connection by taking one input datastream from an application and split that data stream in to one or moresubflows. Control information is included in the subflows to allow thedata stream to be reassembled and delivered to the application runningon the other end of the link. In the cases described herein, the proxyserver 150 running on the mobile router 20 will produce a data streamthat is to be sent to the proxy server 170 running in the data centre140. The MPTCP connection, at the mobile router 20 end, takes the datastream originating from the mobile proxy 150 and splits that data streamin to two or more subflows. Control information is included in each ofthe subflows so that the data stream can be reassembled at the datacentre end of the MPTCP connection. The MPTCP connection can duplicate aparticular subflow so that a particular subflow can be sent over morethan one path. This can be used to provide resilience to the connection.In the other direction, the parent proxy 170 running in the data centrewill produce a data stream that is to be sent to the mobile proxy 150.The MPTCP connection, at the data centre end, takes the data streamoriginating from the parent proxy 170 and splits that data stream in totwo or more subflows. Control information is included in each of thesubflows so that the data stream can be reassembled at the mobile router20 end of the MPTCP connection. The MPTCP connection can duplicate aparticular subflow so that a particular subflow can be sent over morethan one path. This can be used to provide resilience to the connection.

The control information that is included in the subflow is included inthe TCP options of the individual TCP connection that forms theindividual subflow. Each data packet sent over the subflow has a subflowsequence number and a data sequence number associated with that datapacket. The subflow sequence number is a used at a subflow level toensure that transmissions sent within that subflow are receivedcorrectly. The subflow sequence number is an identifier that identifiesthe sequence of data sent over a particular path. The data sequencenumber is used by the receiver to ensure in-order delivery of the dataflow to the application layer. As discussed above, in the current case,this means the delivery of data to the proxy server located at each endof the link between the train 10 and the data centre 140.

A range of the data sequence number is mapped to a particular subflowfor a particular length of data. This mapping maps a segment of the datasequence number on to the subflow sequence number of a particular path.The receiving device can therefore reassemble the sent data flow byreordering the received data so that the data sequence numbers are inorder. The data sequence number is an identifier that identifies thesequence of the data flow sent over the MPTCP connection.

The data that is requested by the end-user device 32, 33 is requested bythe mobile proxy 150 from the parent proxy 170 using a MPTCP connectionover the multiple paths that are available to the mobile proxy. Theparent proxy 170 can then request that data from the remote server 160using conventional protocols that the remote server 160 supports. Datareceived for the end-user device 32, 33 at the parent proxy 170 istransmitted to the mobile proxy 150 using the MPTCP connection over themultiple paths. It is then transmitted by the mobile proxy 150 to theend-user device 32, 33 using conventional protocols that are supportedby the end-user device 32, 33. As the MPTCP connection is establishedonly between the local 150 and parent 170 proxies the MPTCP connectionis hidden from both the end-user devices and the remote servers on theinternet. This means that the end-user devices can receive the benefitsof using an MPTCP connection without needing to be aware that such aprotocol is being used.

By the use of two proxies in series, both of which support MPTCP, oranother multiple path transport layer protocol, on the connectionbetween them, the connection from the end-user device to the internetcan benefit from MPTCP even if one or both of the end-user device andthe internet end point do not support MPTCP.

The communication by end-user device 32 with remote server 160 isexplained below with reference to FIG. 2.

The end-user device 32 attempts to form a connection with a remoteserver 160 to request data from the remote server 160. This connectionattempt is sent over a wireless link 200 by the end-user device 32 usinga radio transceiver connected to antenna 34. It is received overwireless link 200 by mobile router 20 using a radio transceiverconnected to antenna 31. The mobile proxy 150 intercepts the connectionattempt and masquerades as the remote server 160. The TCP user sessionthat originates from the end-user device 32 is therefore terminated atthe mobile proxy 150. The end-user device 32 believes that it hasestablished a connection to the remote server 160 when in fact it hasestablished a connection with mobile proxy 150.

Mobile router 20 can establish multiple data connections using themultiple radio transceivers that are each attached to a separate antenna40, 50. These data connections are established with respective basestations. Whilst it is not shown in FIG. 2, the mobile router 20 couldbe connected to a slave router 180 to provide at least one of the dataconnections as discussed with reference to FIG. 1 above.

Mobile proxy 150 establishes a connection 210 with parent proxy 170using the MPTCP protocol. Within the MPTCP connection 210 there areseparate subflows 211, 212. There is at least one subflow for eachseparate path defined by the separate data connections. The separatepaths from the mobile router 20 are identified as being separate pathsbecause they each have a different network layer address. For example,they have different IP addresses. The connection 210 established toparent proxy 170 is used to by the mobile proxy 150 to request the datathat the end-user device 32 has requested. The mobile proxy 150therefore requests the data from parent proxy 170 on behalf of theend-user device 32. When the mobile proxy 150 requests this informationit identifies as, the mobile proxy 150 at the transport layer.

The parent proxy 170 receives the request for data on the remote serverfrom mobile proxy 150 over the MPTCP connection 210. The parent proxy150 intercepts the request from the mobile proxy 150 and masquerades asthe remote server 160. The TCP user session that originates from themobile proxy 150 is therefore terminated at the remote proxy 170. Themobile proxy 150 believes that it has established a connection to theremote server 160 when in fact it has established a connection withparent proxy 170.

The parent proxy 170 establishes a connection 220 to remote server 160to request the data from remote server 160 on behalf of the mobile proxy150 and so indirectly, on behalf of the end-user device 32. Theconnection 220 established between parent proxy 170 and remote server160 can be made using conventional protocols and does not need to be aconnection that uses a multipath transport layer protocol.

The remote server 160 responds to the request for data by sendingresponse data to parent proxy 170 over the connection 220 establishedbetween the remote server 160 and the parent proxy 170. When the parentproxy 170 has received this response data, the parent proxy 170 respondsto the request sent by the mobile proxy 150 on behalf of the end-userdevice 32 over the MPTCP connection 210. The parent proxy 170 will usethe multiple subflows 211, 212 of the MPTCP connection 210 that havebeen established over the respective paths. In this response by theparent proxy 170 to the mobile proxy 150 will be included the responsedata sent by the remote server 160.

When the mobile proxy 150 has received this response data, the mobileproxy 150 responds to the request sent by the end-user device 32. Themobile proxy 150 includes the response data send by the remote server160 in the response sent to the end-user device 32 over wirelessconnection 200. The wireless connection 200 could be a wired connectionif the train comprises a wired network to which end-user devices 32, 33can connect using a wired network adapter.

Whilst the above description has focused on end-user devices 32, 33 thatconnect via a wireless connection, it should be readily apparent thatany host device that requires access to server remote from the on-boardenvironment could use the above described communication system. Forexample, the host device could be a device that provides data to theon-board vehicle systems. The host device could provide telemetry datato a remote server such as running time or vehicle position.

The applicant hereby discloses in isolation each individual featuredescribed herein and any combination of two or more such features, tothe extent that such features or combinations are capable of beingcarried out based on the present specification as a whole in the lightof the common general knowledge of a person skilled in the art,irrespective of whether such features or combinations of features solveany problems disclosed herein, and without limitation to the scope ofthe claims. The applicant indicates that aspects of the presentinvention may consist of any such individual feature or combination offeatures. In view of the foregoing description it will be evident to aperson skilled in the art that various modifications may be made withinthe scope of the invention.

1. A communications system for providing data communication to avehicle, the communications system comprising: a mobile transport layerproxy located on the vehicle; a parent transport layer proxy locatedremote from the vehicle; the mobile transport layer proxy beingconfigured to: accept a transport layer connection with a host device,the transport layer connection being addressed to a remote server; andcommunicate with the parent transport layer proxy via multiple pathsusing a multipath transport layer protocol to communicate on behalf ofthe host device whilst identifying as the mobile transport layer proxy;and the parent transport layer proxy being configured to: communicatewith the mobile transport layer proxy using the multipath transportlayer protocol; and communicate with the remote server whilstidentifying as the parent transport layer proxy to communicate on behalfof the mobile transport layer proxy to permit the host device tocommunicate with the remote server.
 2. A communications system asclaimed in claim 1, wherein the parent transport layer proxy isconfigured to accept a connection with the mobile transport layer proxythat is addressed to the remote server.
 3. A communications system asclaimed in claim 1, wherein the parent transport layer proxy isconfigured to communicate with the mobile transport layer proxy viamultiple paths using the multipath transport layer protocol.
 4. Acommunications system as claimed in claim 1, wherein the mobiletransport layer proxy is configured to accept the transport layerconnection with the host device by intercepting a transport layersession originating from the host device that is addressed for theremote server.
 5. A communications system as claimed in claim 4, whereinthe mobile transport layer proxy is configured to accept the transportlayer connection with the host device by masquerading as the remoteserver and terminating the transport layer session originating from theon-board device at the mobile transport layer proxy.
 6. A communicationssystem as claimed in claim 1, wherein the parent transport layer proxyis configured to intercept a transport layer session originating fromthe mobile transport layer proxy that is addressed for the remoteserver.
 7. A communications system as claimed in claim 6, wherein theparent transport layer proxy is configured to masquerade as the remoteserver and terminates the transport layer session originating from themobile transport layer session at the parent transport layer proxy.
 8. Acommunications system as claimed in claim 1, wherein the mobiletransport layer proxy is connected to a plurality of radio transceivers,each radio transceiver is configured to establish a respective wirelessdata connection to equipment located remote from the vehicleindependently of the other radio transceivers, and each one of the dataconnections is one of the multiple paths.
 9. A communications system asclaimed in claim 8, wherein the plurality of radio transceivers arelocated on the vehicle.
 10. A communications system as claimed in claim8, wherein each radio transceiver establishes the respective dataconnection with a different base station located remote from thevehicle.
 11. A communications system as claimed in claim 8, wherein thebase station comprise one of a number of wayside base station next to apath taken by the vehicle.
 12. A communications system as claimed inclaim 11, wherein the vehicle is a train and the path taken by thevehicle is a railway track.
 13. (canceled)
 14. (canceled)
 15. Acommunications system as claimed in claim 8, the communication systemcomprising a mobile router located on the vehicle, the mobile routercomprising the plurality of radio transceivers.
 16. A communicationssystem as claimed in claim 15, wherein the mobile transport layer proxyforms part of the mobile router and the mobile router communicates withthe parent transport layer proxy via multiple paths using the multipathtransport layer protocol.
 17. A communications system as claimed inclaim 1, wherein at least one separate subconnection of the multipathtransport layer protocol is established over each of the multiple paths.18. A communications system as claimed in claim 17, wherein a separatesubconnection of the multipath transport layer protocol is establishedover each of the multiple paths.
 19. A communications system as claimedin claim 17, the mobile transport layer proxy being configured to dividea data stream for transmission to the parent transport layer proxy in toa number of substreams at least equal to the number of paths and send aduplicated or different substream over each of the subconnections.
 20. Acommunications system as claimed in claim 17, wherein the mobiletransport layer proxy is configured to divide a data stream fortransmission to the parent transport layer proxy in to a number ofsubstreams equal to the number of paths and send a different substreamover each of the subconnections.
 21. A communications system as claimedin claim 19, wherein the substreams are formed of data packets and themobile transport layer proxy is configured to incorporate a data streamidentifier in to each data packet, the data stream identifier indicatingthe position of the data packet in the data stream.
 22. A communicationssystem as claimed in claim 1, wherein the multipath transport layerprotocol is Multipath Transmission Control Protocol (MPTCP).
 23. Acommunications system as claimed in claim 17, wherein the separatesubconnections are separate subflows of the MPTCP.
 24. (canceled)
 25. Acommunications system as claimed in claim 1, wherein the parenttransport layer proxy does not move with the vehicle.
 26. (canceled) 27.(canceled)
 28. (canceled)